1. Field of the Invention
The present invention pertains to techniques for coupling members while permitting mutual relative movement. More particularly, the present invention relates to techniques for anchoring support structures in wells or the like, such as liner hangers utilized to support liners while they are being connected in place. As used herein, wells are meant to include without limitation all types of holes in the ground, including for example oil and gas wells, water wells, ventilation shafts, fluid communication conduits, tunnels and the like. While the invention is disclosed herein as embodied in a liner hanger used in oil and gas wells for supporting liners while the liners are being cemented in place, the present invention may be provided in any appropriate form to support any other type of equipment, for example.
2. Brief Description of the Prior Art
Liner hangers for positioning and supporting liners for cementing in oil and gas wells, for example, are known having an array of slips carried about a generally tubular member which also features corresponding wedging, or cone, surfaces. Setting the liner hanger involves positioning the wedges and slips so that the wedges are generally radially, or transversely, aligned with corresponding slips to wedge the slips radially outwardly against the surrounding well surface, usually the surface of casing or another liner already positioned within the well. In this way, the liner hanger is anchored to the well and supported thereby, and in turn can support the liner being cemented in position. During the process of running in the liner and liner hanger within the well, the liner hanger must be configured to avoid such radial alignment of the slips and wedges. Consequently, the setting operation also includes at least one step to move the liner hanger out of the running in configuration so that the slips and wedges may be appropriately aligned for anchoring to the well. In hydraulically set liner hangers, one or more frangible parts may be broken to move the liner hanger out of the running in configuration. A mechanically set liner hanger may employ the closing of a latching device or the like whereby the liner hanger may be moved to the set configuration. In such types of liner hangers, initiation of the setting procedure may be irreversible so that, if the setting procedure is inadvertently initiated, or if the apparatus becomes hung up within the well, it may become impossible to reposition the liner hanger or to retrieve the liner hanger and associated equipment to clear the well.
A pin-and-slot assembly, in the form of a J-latch for example, may be utilized to maintain the liner hanger in its running in configuration by serving to latch a slip frame, carrying the slips, to the tubular member, carrying the wedges, in the running in configuration. The liner hanger may be moved to a set configuration by maneuvering the pin or pins relative to the slot or slots of the J-latch, the slip frame being attached to a friction device such as provided by drag springs or the like which engage the surrounding well surface and permit selected movement of the tubular member relative to the slip frame. If necessary, the liner hanger may be maneuvered out of the set configuration and the J-latch repositioned to maintain the liner hanger in its running in configuration for repositioning or retrieval of the liner hanger, for example.
Setting a liner hanger fitted with a J-latch, however, includes rotating and longitudinally moving the tubular member with the wedges relative to the drag springs. Since the slip frame and slips are connected to the drag springs, prior J-latch liner hangers have been constructed with the slips rotationally offset from the corresponding wedges in the running in configuration to accommodate relative rotation between the wedges and slips in the setting operation so that the wedges may be rotationaly aligned with corresponding slips in the set configuration. Prior drag spring assemblies also supported the slip frame and slips and held them against longitudinal movement relative to the well, as the J-latch would be manipulated, requiring substantial frictional forces between the drag springs and surrounding well surface. It is desirable and advantageous to provide a mechanically set and retrievable liner hanger which may be run in and maintained throughout the setting operation with the slips rotationally aligned with the corresponding wedges. It is also desirable and advantageous to provide a coupling between the slip assembly and the drag spring assembly which permits limited longitudinal movement therebetween so that the drag spring assembly need not bear the weight of the slip frame, or hold down the slips during the setting operation.